Analysis of nuptiality in small populations requires that constraining influences of demographic and genealogical structure be distinguished from mate choice itself. An important consideration in small populations in the occurrence of consanguineous marriage. The goal of the proposed research is to apply to two small population isolates procedures which will (1) elucidate opportunities for marriage of relatives, and (2) measure the strength of preferences which govern choice of marriage partners. These procedures will be used to examine both the effects of explicitly stated marriage rules, and those of preferences which can only be inferred from observed distributions of marriages. Mate choice will be compared over time in one of the populations in order to assess the effects of modernization on mate choice. Simulation experiments will be used to examine effects of mate choice on the development of genealogical structure. Improvements will be made to a procedure which makes estimates of missing vital dates in a genealogy